If the rectangle is made up of a stroke path, I would select it and press <F2> to edit nodes. Select the nodes that make up the line you want to remove and select "Break path at selected nodes". You should then be able to select the individual nodes and move the line away from the rest of the rectangle. You could then select both nodes from the line that you want to delete and press delete.
I imagine there is a more fluid way to do this, but I don't know of it.
Beginners' Questions I need serious help
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I want to remove one line from this rectangle but don't know how how I even tried path difference. Is there any any way to easily do this?
If the rectangle is made up of a stroke path, I would select it and press <F2> to edit nodes. Select the nodes that make up the line you want to remove and select "Break path at selected nodes". You should then be able to select the individual nodes and move the line away from the rest of the rectangle. You could then select both nodes from the line that you want to delete and press delete.
I imagine there is a more fluid way to do this, but I don't know of it.
Please post the file that has the problem.